Supermarkets group Sainsbury said it is to create 20,000 new permanent and part-time jobs over the next three years, the bulk of them in the north of England and in Scotland.Historically, Sainsbury has had a stronger presence in the south of England but the company is planning to beef up its presence north of the Watford Gap. In November 2010 it announced plans to open 1.5m square feet of retail space in the current financial year.The commitment to take on new staff extends Sainsbury's pledge to create 6,500 jobs in 2011 and follows hot on the heels of plans announced yesterday by rival supermarket chain Morrisons to create 6,000 new jobs this year.Sainsbury chief executive Justin King made the announcement at an employment summit being hosted by prime minister David Cameron.